q/* Nautilus Pompilius. 61 



sists, I think it better not to refer to and complete my former 

 observations, but, with better means at my command, to describe 

 continuously what I have observed. Some points must still re- 

 main in obscurity, where the investigation is confined to specimens 

 preserved in spirit. It is therefore to be wished that these and 

 other peculiarities in the anatomy of the animals may sooner or 

 later be investigated by careful anatomists located in our colonies. 

 I consider myself fortunate in having brought to light some addi- 

 tional facts in the anatomy of the Nautilus, which has been ren- 

 dered by such an excellent investigator as R. Owen an object of 

 common interest to all zoologists. 



I. — External form of the male Nautilus Pompilius, L, 



In the male and female Nautilus the general disposition of 

 the body is the same. It consists of two principal portions, an 

 anterior firmer and more muscular, comprising the organs of 

 motion and of the senses, and including the horny beak, and a 

 thin membranous sac in which the viscera are contained. This 

 sac at its anterior part passes into a firm dermal lobe named the 

 mantle, and opens externally under the first portion by the fun- 

 nel formed of two lobes which lie upon one another*. 



In the anterior portion we distinguish in the first place the 

 hood. This is the name given by Owen to a membranous disk 

 which the aperture of the shell encloses ; it is higher behind, and, 

 gradually becoming thinner forward, has the form of a cap. It 

 is about 1 decimeter in length, and at its broadest part in the 

 male has a breadth of from 7^ to 9 centimeters. At the back 

 part the hood is excised in the middle; this excision, about 4 

 centimeters in depth, corresponds to the turn of the shell which 

 projects into its aperture. A longitudinal furrow on the upper 



* Sometimes the right lobe of the funnel, sometimes the left, lies upon 

 the other. This opening of the funnel below is a remarkable peculiarity, 

 since in the other Cephalopods (the dibranchiate) the funnel forms a 

 closed canal. I had already drawn attention to the fact, that this dispo- 

 sition in the tetrabranchiate Cephalopods (Nautilus) may be regarded as a 

 persistent embryonal structure, since, according to Kolliker's observations, 

 the funnel in the dibranchiate Cephalopods is, in the beginning, formed of 

 two lateral parts which are distinct. (Entwickelungsgeschichte der Cepha- 

 lopoden von Dr. A. KoUiker. Zurich, 1843, 4to, s. 41.) 



I will here repeat the remark, in passing, that the aperture, by which, 

 according to Owen, the mantle is perforated for the passage of the funnel 

 (Memoir on the Nautilus, p. 9), has no existence. The mantle has a 

 uniform free margin, on which the extremity of the funnel rests. I state 

 this, because the second edition of Owen's Lectures on the Comp. Anat. of 

 the Invertebrated Animals, which appeared after my * Contributions,' still 

 retains, by some oversight, the passage, p. 5/9, of the former edition : 

 " The margin of the mantle is perforated below for the passage of the mus- 

 cular expiratory and excretory tube called the funnel" (1843, p. 316). 



